Fluidized bed reactors are often commonly used to gasifier carboneous materials such as coal. An example of such a gasifier is provided in U.S. patent application Ser. No. 13/532,769. A characteristic of such a gasifier is that the operating temperature of the gasifier is just below the melting point of the ash, and as such these gasifiers are called non-slagging gasifiers.
In the gasifier, solid feed stock reacts with steam and oxygen and is gasified to produce a synthesis gas (“Syngas”) product containing hydrogen, carbon monoxide, carbon dioxide and methane. In addition to the partial oxidation of solid feed stock, the following reactions take place in the gasifier:Water gas shift reaction: CO+H2O→CO2+H2  Rx(1)Methanation (CO): CO+3H2→CH4+H2O  Rx(2)Methanation (CO2): CO2+4H2→CH4+2H2O  Rx(3)
Syngas also comprises a significant amount of methane (CH4). The amount of methane produced varies depending on reaction conditions and the composition of the feed material. For example, with coal as the feed material, and at pressures of 40 Bar and above, methane can be 15-20% of the dry syngas output. This amount of methane represents an economically significant portion of the useful syngas carbon and heating value. Yet for many applications, e.g. the use of syngas as raw material for chemical synthesis of methanol, methane is unwanted.
Currently, methane is separated and reformed to achieve economic yields of CO and H2 from the original gasifier feedstock. The reforming step requires expensive equipment, and consumes significant amount of oxygen and steam. Furthermore, to maintain catalyst activity, the methane must be purified, also a very expensive step.
Therefore, there is a need in the industry for an improved process whereby methane in syngas can be converted into CO and H2 without the drawbacks of the prior art processes.